Electromagnetic induction has provided reliable, predictable, and cost-effective heat treatment results for decades. Recently-developed inverter technology, providing instantaneous and calculated frequency control during heating, is dramatically advancing the heat treatment quality and equipment capability that induction heat treatment systems can deliver. This paper presents the many advantages of the technology in numerous real-world induction heat treatment applications, particularly in the scan hardening of shafts and shaft-like components. Coupled electromagnetic-thermal finite element analysis simulation results are utilized throughout to graphically and numerically illustrate the revolutionary nature of this new technology.